This invention relates to improved weld retention for press fit joints.
Press fit joints are utilized in many applications. In a typical press fit joint, an outer part has a bore with an inner diameter slightly less than the outer diameter of an inner part. The inner part is forced into the bore, and the larger diameter of the inner part holds the inner part within the outer part.
However, the press fit alone is inadequate for many applications. Thus, press fit joints are often augmented by a secondary locking mechanism. The ability to hold a press fit joint is limited by the size, material and certain manufacturing characteristics of the joint parts. This is particularly true in structural applications where there may be stresses upon the inner and outer parts.
The selection of a particular type of secondary locking mechanism is based in large part on the materials of the inner and outer parts. If both the inner and outer parts are of materials which can provide an adequate weld joint, then a weld may be utilized as the secondary locking mechanism. However, if one or both of the parts is iron, then a dowel pin is often utilized. Iron is often not capable of providing an adequate weld joint. Dowel pins extend through the outer parts and into the inner part to provide the secondary locking mechanism. However, dowel pins require machining after assembly, and thus set high manufacturing costs.
If the inner part is iron and the outer part is steel, then a puddle weld may be utilized. A puddle weld provides a bond weld on the steel part, while the weld integrity on the outer iron member is not as important. Instead, in the iron part, the puddle weld merely provides a stop. In such an application, the puddle weld provides a shear pin which does not typically bond to the outer iron member.
However, a reliable cost effective secondary locking mechanism has not been provided when both of the press fit parts are iron.